Continuity 35 



case of matter and ether, not only is even 

 the densest matter excessively porous 

 and discontinuous, with vast interspaces 

 in and among the atoms, but the consti- 

 tution of matter is such that there appears 

 to be no displacement in the ordinary 

 sense at all; the ether is itself so modified 

 as to constitute the matter in some way. 

 Of course that portion moves, its inertia 

 is what we observe, and its amount de- 

 pends on the potential energy in its 

 associated electric field, but the motion 

 is not like that of a foreign body, it 

 is that of some inherent and merely 

 individualised portion of the stuff itself. 

 Certain it is that the ether exhibits no 

 trace of viscosity. 1 



Matter in motion, Ether under strain, 

 constitute the fundamental concrete 

 things we have to do with in physics. 

 The first pair represent kinetic energy, 

 the second potential energy; and all the 



1 For details of my experiment on this subject see Phil. 

 Trans. Roy.Soc. for 1893 and 1897; or a very abbreviated 

 reference to it, and to the other matters above-mentioned, 

 in my small book The Ether of Space. 



